Finding the Least Common Denominator using Cuisenaire Rods
1. To find the least common denominator for the fractions
and
:
a. Choose rods which represent both of the denominators.
Here the denominators are 2 (red rod) and 3 (light green rod).
b. Create a train of red rods and a train of light green rods until
they are the same length. A train is when you line up the rods
end-to-end.
c. Count the total number of rods used for each train. Here we
used 3 red rods and each red rod is worth 2 units. Thus the red
train is 3 × 2 or 6 units long. We used 2 light green rods and
each light green rod is worth 3 units. Thus the light green train
is 2 × 3 or 6 units long. Thus the least common denominator is
6.
Red Rod = 2
Red Rod = 2
Red Rod = 2
Light Green Rod = 3
Light Green Rod = 3
Dark Green Rod = 6
2. Find the Least Common Denominator for
and
.
a. The denominators are 4 (purple rod), and 3 (light green rod).
b. Create a train for the purple rods and a train for the light
green rods until they are the same length.
c. There will be 3 purple rods. Thus 3 × 4 = 12.
There will be 4 light green rods. Thus 4 × 3 = 12.
Thus the Least Common Denominator will be 12.
Purple Rod = 4
Purple Rod = 4
Purple Rod = 4
LG Rod = 3
LG Rod = 3
LG Rod = 3
LG Rod = 3
Rorange Rod = 12
Finding the Least Common Denominator using Cuisenaire Rods
Sketch a picture to show how you found the LCD using
Cuisenaire Rods.
1.
2.
3.